THEORY OF ADJUSTMENT 



17 



North heading by East heading by South heading by West heading by 

 compass. compass. compass. compass. 



E. Dev. •'• Dev. 



Compass 

 Needle 

 Fore-and-Aft "B" 

 Permanent Magnetic 

 Field 

 No deviation Maximum devia- No deviation Maximum devia- 

 ( change in di- tion easterly. (change in di- tion westerly, 



rective force rective force 



only). only). 



FiGURB 9. — Force diagrams for fore-and-aft permanent B magnetic field. 



North heading by East heading by South heading by West heading bj' 

 compass. compass. compass. compass. 



E. Dev. 



Athwartship "C" 

 Permanent Magnetic 

 Field 

 Maximum devia- No deviation. Maximum devia- No deviation, 



tion easterly. tion westerly. 



FiGDRH 10. — Force diagrams for atliwartship permanent C magnetic field. 



